There is a brake release device for a work vehicle with a negative-type parking brake known in the related art, in which brake release pressure is supplied from a hydraulic power source so as to release the parking brake and the brake release pressure is stopped supplying so as to operate the parking brake (refer to, for instance, patent reference literature 1). The brake release device in patent reference literature includes a first and a second clutch devices in a transmission, engages both of the clutch devices in response to an operation instruction for parking brake so as to lock the transmission, and activates the parking brake.    Patent reference literature 1: Japanese Laid Open Patent Publication No. 2002-79931